Sedimentation tank with raking structure

Abstract

A raking structure for moving settled solids to a discharge opening in the bottom of a sedimentation tank is disclosed herein. The raking structure consists of a rotatable member and a rake arm pivoted on the rotatable member along an inclined pivot axis with a counterweight connected to the rake arm through cable means so that the torque load required to cause the arm to pivot can be varied. The rake arm may also have means for varying the buoyancy of the rake arm and thereby vary the torque or moment compound required to pivot the rake arm with respect to the rotatable member.

What is claimed is: 
     
       1. A raking structure for moving settled solids to a discharge opening in the bottom of a sedimentation tank comprising a rotatable member located in said tank and driven about a vertical axis, a rake arm supported at one end on said rotatable member on a pivot axis that is angularly related to said vertical axis and a horizontal plane, cable means having one end connected to said rake arm at a location spaced from said pivot axis, said cable means being located substantially along a plane extending through said vertical axis, a support located above said pivot axis on said rotatable member with said cable means entrained over said support, and counterweight means connected to an opposite end of said cable means, said cable means and counterweight means functioning to vertically pivot said rake arm through an angle Q, in response to a predetermined resistance to the rotation of said rake arm, said angle Q being defined by the equation:   Tan Q=(W-C)/T C/T     where:   W=the component of moment acting on said rake arm, due to the vertical force of the weight of said rake arm,   C=the component of moment acting on said rake arm, due to said cable means and counterweight means, and,   T=the component of moment acting on said rake arm due to said predetermined resistance.   
     
     
       2. A raking structure as defined in claim 1, in which said support includes a drum rotatable about a horizontal axis on said rotatable member. 
     
     
       3. A raking structure as defined in claim 1, further including means on said rake arm for varying the buoyancy of said rake arm. 
     
     
       4. A raking structure as defined in claim 1, further including second cable means having one end fixed to said rake arm and an opposite end fixed to said rotatable member, said second cable means defining a lowermost position for said rake arm. 
     
     
       5. A raking structure as defined in claim 1, further including indicating means for indicating the position of said rake arm with respect to said tank. 
     
     
       6. A raking structure for moving settled solids to a discharge opening in the bottom of a sedimentation tank comprising a rotating member located in said tank and driven about a vertical axis, a rake arm supported at one end on a pivot axis that is angularly related to said vertical axis and a horizontal axis so that said rake arm is pivoted about said axis when a predetermined torque load is developed on said arm and alterable means connected to said rake arm for determining said predetermined torque load, said means connected to said rake arm for varying said predetermined torque load functioning to vertically pivot said rake arm through an angle Q, in response to a predetermined resistance to the rotation of said rake arms, said angle Q being defined by the equation:   Tan Q=(W-C)/T     where:   W=the component of moment acting on said rake arm, due to the vertical force of the weight of said rake arm,   C=the component of moment acting on said rake arm, due to said alterable means connected to said rake arm for determining said predetermined torque load, and   T=the component of moment acting on said rake arm due to said predetermined resistance.   
     
     
       7. A raking structure as defined in claim 6, in which said last means includes an inflatable member secured to the outer end of said rake arm. 
     
     
       8. A raking structure as defined in claim 6, in which said last means includes cable means having one end connected to said rake arm and counterweight means connected to an opposite end of said cable means, said rotating member having a drum supported thereon with an intermediate portion of said cable means entrained over said drum.